This invention relates to a cutting machine, and especially, although not limited to, a cutting machine suitable for cutting a CSP (chip size package) substrate, which has CSP formed in each of plural rectangular areas demarcated by cutting streets arranged in a lattice pattern, along the cutting streets.
CSP is practically used as a semiconductor device suitable for use in small-sized electronic equipment, such as a mobile phone and a laptop personal computer. The CSP is usually produced in the following manner: A plurality of rectangular areas are demarcated by cutting streets arranged in a lattice pattern on a suitable substrate, such as a synthetic resin substrate, and a chip such as IC or LSI is disposed in each of the rectangular areas to form CSP""s. A single substrate having a plurality of CSP""s formed thereon is generally called a CSP substrate. Then, the CSP substrate is cut along the cutting streets to form individual CSP""s.
A cutting machine including a chuck table to be reciprocated between one end position and the other end position, and cutting means for cutting a workpiece held on the chuck table, namely, a CSP substrate, is used to cut the CSP substrate along cutting streets. The cutting means is composed of a disc-shaped rotary cutting blade containing diamond grains. The cutting means is equipped with cooling fluid jetting means for jetting a cooling fluid which may be pure water. While the chuck table is moving forward and/or backward, the rotary cutting blade is caused to act on the CSP substrate on the chuck table, performing cutting of the CSP substrate. The rotary cutting blade is rotated in a predetermined direction, for example, a direction in which the site to act on the CSP substrate moves in the forward moving direction of the chuck table. A reciprocating mechanism for reciprocating the chuck table as required includes a rotatable threaded shaft extending in a reciprocating direction, and an internal thread member screwed on the threaded shaft, with the chuck table being mounted to the internal thread member. The threaded shaft and the internal thread member are so-called precision machine elements, and adhesion of swarf and/or the cooling fluid to such elements should be avoided. Owing to the rotation of the rotary cutting blade, swarf and the cooling fluid are scattered mainly to one side as viewed in the reciprocating direction of the chuck table. For example, when the rotary cutting blade is rotated in a direction in which the site to act on the CSP substrate moves in the forward moving direction of the chuck table, swarf and the cooling fluid are scattered to the downstream side as viewed in the forward moving direction of the chuck table. Part of the cooling fluid turns into a mist, and also scatters to the upstream side as viewed in the forward moving direction of the chuck table. Thus, bellows means is disposed at least on one side, usually on both sides, as viewed in the reciprocating direction of the chuck table, to cover the precision machine elements such as threaded shaft. When the chuck table is making a forward or backward motion, the bellows means disposed downstream in the forward moving direction of the chuck table is contracted, while the bellows means disposed upstream in this direction is expanded. When the chuck table is making a backward motion, the bellows means disposed upstream in the forward moving direction of the chuck table is contracted, while the bellows means disposed downstream in this direction is expanded.
The above-described conventional cutting machine has the following problems to be solved: At the edge of a CSP substrate, there are selvedge portions where no CSP""s are formed. Particularly when the CSP substrate is cut, such selvedge portions are scattered, as relatively large swarf, over the bellows means disposed on one side as viewed in the reciprocating direction of the chuck table, for example, downstream side as viewed in the forward moving direction of the chuck table when the rotary cutting blade is rotated in a direction in which the site to act on the CSP substrate moves in the forward moving direction of the chuck table. The relatively large swarf that has scattered over the bellows means tends to inhibit the smooth contraction and expansion of the bellows means. Since the bellows means needs to be smoothly contracted and expanded, it is normally formed of a cloth or a similar material. Thus, the relatively large swarf that has scattered over the bellows means has not a little chance of causing damage, such as a hole, to the bellows means.
A principal object of the present invention is to provide a novel and improved cutting machine which effectively prevents scattered swarf from inhibiting the smooth contraction and expansion of bellows means or from damaging the bellows means.
The inventors of the present invention have disposed a protective sheet for covering the upper surface of the bellows means, and have designed the protective sheet to be wound up and wound off, as desired, in accordance with the reciprocation of the chuck table, accordingly, in accordance with the contraction and expansion of the bellows means. By so doing, they have found that the above principal object can be attained.
That is, according to the present invention, there is provided as a cutting machine solving the above-mentioned principal technical problem, a cutting machine including a chuck table to be reciprocated between one end position and the other end position; bellows means disposed at least on one side of the chuck table as viewed in the reciprocating direction of the chuck table, fixed at one end to the chuck table, and fixed at the other end to a stationary member; and cutting means for cutting a workpiece held on the chuck table, and configured such that
when the chuck table is moved forward and/or backward, the cutting means acts on the workpiece held on the chuck table to cut the workpiece, whereupon swarf scatters at least on the one side as viewed in the reciprocating direction of the chuck table, and when the chuck table is moved forward or backward, the bellows means is contracted, while when the chuck table is moved backward or forward, the bellows means is expanded; and wherein
a protective sheet for covering the upper surface of the bellows means is disposed, one end of the protective sheet is reciprocated in accordance with the reciprocation of the chuck table, and the other end of the protective sheet is connected to winding means, so that when the chuck table is moved forward or backward, the protective sheet is gradually wound up by the winding means in accordance with the forward movement or backward movement of the chuck table, and when the chuck table is moved backward or forward, the protective sheet is gradually wound off from the winding means in accordance with the backward movement or forward movement of the chuck table.
Preferably, the winding means is composed of a shaft member mounted rotatably, and the protective sheet has a wrap tendency to be wrapped about the shaft member when no force is exerted on the protective sheet, and the protective sheet is gradually wound up by the shaft member because of the wrap tendency of the protective sheet when the chuck table is moved forward or backward. Swarf release means can be disposed for releasing swarf, which has adhered to the surface of the protective sheet, from the protective sheet wound up by the winding means. Preferably, the swarf release means is composed of a release plate disposed adjacent to the winding means, and the release plate has a tip edge contacting or approaching the surface of the protective sheet at a position immediately before the protective sheet is wound up by the winding means. In a preferred embodiment, swarf transport means is disposed downstream from the winding means as viewed in the forward moving or backward moving direction of the chuck table, and the swarf release means guides swarf, which has been released from the surface of the protective sheet, onto the swarf transport means. The swarf transport means can be composed of an endless conveyor belt mechanism. Preferably, the cutting means is equipped with cooling fluid jetting means; the endless conveyor belt mechanism includes an endless belt having many drainage holes formed therein, and drainage means disposed below the endless belt; and a cooling fluid having flowed in onto the endless belt is flowed downward into the drainage means through the drainage holes. A swarf collection vessel can be disposed, and swarf collection means for releasing swarf transported by the endless belt and guiding them into the swarf collection vessel can be disposed. The swarf collection means can be composed of brush means acting on the surface of the endless belt.